Various imaging technologies may be used to create detailed images of internal organs and internal physical features. For example, ultrasound utilizes high frequency sound waves that are reflected by internal tissue at different intensities to produce images viewable in real-time on a computer display. Ultrasound is commonly used for safely imaging a developing foetus in a pregnant woman, for example. Thermography utilizes differences in regional temperatures to create an infrared digital image of tissue, and is sometimes used in screening breast tissue for identification of potentially cancerous breast tumours. Tomography utilizes x-rays to provide imaging of a single plane or slice of tissue. One type of tomography is a Computed Axial Tomography scan (more commonly known as a CAT scan) which utilizes helical tomography to produce a series of thin slice or section images of a body to generate a virtual three-dimensional image of the inside of a body. While effective for screening certain types of tissues inside the body, existing imaging technologies and image processing techniques are still limited when it comes to screening for certain types of tissues located deep within the body which are substantially similar to the surrounding tissue.
Detection and localization of prostate cancer is one such challenge. Prostate cancer is the most common form of cancer diagnosed in men, with roughly 241,740 new cases in 2012 in the United States alone. Furthermore, prostate cancer is the second leading cause of cancer death in males in the United States, with an estimated 28,170 deaths in 2012. Similar per capita rates of deaths from prostate cancer can be found in other jurisdictions. Given that the median patient survival time for metastatic prostate cancer ranges from about 12.2 to 21.7 months, early clinical diagnosis of prostate cancer is key to improving the treatment and longevity of patients affected by prostate cancer.
Presently, conventional clinical diagnosis of prostate cancer involves a prostate specific antigen (PSA) screening, where high PSA levels are considered indicative of possible signs of prostate cancer. However, PSA screening has resulted in significant over-diagnosis of men suspected of having prostate cancer but who do not actually require treatment. As a consequence, many men are over-treated with therapies that carry significant risks in themselves. Furthermore, there is still no reliable, widely accepted method of diagnostic imaging for prostate cancer. Although transrectal ultrasound (TRUS) is used routinely as a guide for biopsy, it cannot be used to visualize cancer foci because many tumours in the prostate gland are isoechoic and cannot be easily differentiated from surrounding tissue, resulting in sensitivity and specificity in the range of only around 40-50%. Positron emission tomography (PET) have also been investigated as a potential imaging modality for prostate cancer detection, with a number of different tracers that have shown promise for identifying prostate cancer. However, the spatial resolution achieved using PET may not be adequate to properly localize and detect early stage prostate cancer. T2-weighted magnetic resonance imaging (MRI) has also been investigated for prostate cancer detection, but currently requires highly-qualified subspecialty radiologists to interpret the data due to its weak delineation between cancerous tissue and healthy tissue. Furthermore, in the peripheral zone of the prostate gland, the low T2 signal intensity that is associated with prostate cancer may also be due to a number of noncancerous abnormal conditions such as inflammation and hemorrhaging.
If detected at an early stage, the prognosis for recovery from prostate cancer is excellent. Hence, early detection and the localization of prostate cancer is crucial for diagnosis, as well as treatment via targeted focal therapy. Therefore, what is needed are further improvements in identification of tissues of interest utilizing novel imaging technologies and image processing techniques.